This invention relates to a Hall element capable of being incorporated into an integrated circuit.
Devices of this type are, for example, used in wattmeters to measure an electric current i.sub.N or to form a voltage/current product u.sub.N .multidot.i.sub.N, where, u.sub.N designates the supply voltage of an electric supply system and i.sub.N the electric current used by a consumer of electric energy. Since the current i.sub.N is proportional to the magnetic field H.sub.N it produces, the Hall element indirectly measures the current i.sub.N by determining the magnetic field H.sub.N. Since the output voltage V.sub.H of the Hall element is proportional to the product of i.multidot.H.sub.N, wherein i represents the supply current of the Hall element, the Hall element will also form the voltage/current product u.sub.N .multidot.i.sub.N, if the supply current i of the Hall element, for instance by means of a resistance, is selected proportionally to the supply voltage u.sub.N. In this case the Hall element has to work as a four-quadrant multiplier, as u.sub.N and i.sub.N, and also i and H.sub.N are sine-shaped, thus having positive and negative values.
A vertical Hall element for use in an integrated circuit is known from the publication "The Vertical Hall-Effect Device", R. S. Popovic, IEEE Electron Device Letters, Vol. EDL-5, No. 9, September 1984, pages 357-358. Vertical Hall elements are Hall elements which measure magnetic fields H.sub.N which are oriented parallel to the surface of the Hall element.
A horizontal Hall element for use in an integrated circuit is known from U.S. Pat. No. 4,253,107. Horizontal Hall elements are Hall elements which measure magnetic fields H.sub.N which are oriented perpendicular to the surface of the integrated Hall element.
Little is known, however, about the stability, especially the long-time stability of the Hall elements. See, for example, "Hall Effect Probes and Their Use In a Fully Automated Magnetic Measuring System", M. W. Poole and R. P. Walker, IEEE Transactions on Magnetics, Vol. MAG-17, No. 5, September 81, page 2132.
The object of the present invention is to provide a Hall element for use in an integrated circuit that is stable for long times. It is an objective of the present invention to form such a Hall element by using a technology that enables the manufacture of Hall elements and transistors in a single integrated circuit.